Several types of self-igniting materials are being tested and/or used for dispensable decoy applications to protect defense vehicles including aircraft, ships, tanks, etc. against heat seeking missiles. Included among such materials are activated metals, activated and catalyzed carbon cloth, phosphorous or boron containing wafers or pellets, other non-metallic or metallic pellets or powders and in fact any such material which when exposed to air, instantaneously combines with the oxygen of the air to exothermally form the corresponding material oxide. The heat emitted from the reaction corresponds to the free energy of formation of the metallic or non-metallic oxide formed in the reaction. Many of these materials emit heat in the infra-red region of the electromagnetic spectrum as gray bodies. In some instances, depending upon the material composition or coating applied to the material, they can then selectively emit in a preferred wave band of the infra-red region.
For some decoy applications it would be most desirable to lower the peak temperature of heat emission and increase the dwell time at the lower temperatures without sacrificing the total energy output.
In addition, there are several other applications (e.g., catalysis and controlled bonding processes) where it would be useful to have an expendable body which can either emit heat, or consume oxygen, in a controlled manner.
We have found in laboratory experiments that mixtures of air and an inert gas such as argon will limit the amount or rate of air contacting an activated metal element and cause a reduction in the maximum temperature of emission and give an increase in the dwell time at the lower temperatures. This method, however, in addition to being impractical, presented problems of passivation during the exotherm and markedly reduced the total energy output. It has also been found, as stated in the Baldi U.S. patent application No. 08/152,830, that the addition of chromium to an activated metal element will reduce the peak temperature and extend the lifetime of the element at the lower temperatures but again with a penalty of reducing the total energy output. If by some method the rate of air impinging upon the activated element could be controllably reduced to monitor the kinetics of the oxidation reaction, the objective of lower peak temperature and longer lifetime at the lower temperature could be achieved, providing there was no pronounced effect in reducing the total heat energy output.